Measurement Setup for Physical Unclonable Functions

Abstract

The use of physical unclonable functions (PUFs) to generate fingerprints for authentication of chips or larger electronic systems or for generation of internal cryptographic keys for data transfer is investigated. With the implementation of PUFs, each chip or electronic system has its own identity, which should prevent counterfeiting and “night shift” problems. There are various approaches to creating PUFs, and one of them is the so-called coating PUF, which would open the way to cost-effective and flexible protection during and after chip fabrication. In this work, we present two different capacitance measurement methods for fabricated PUF structures consisting of individual metal-oxide-semiconductor (MOS) capacitors. The goal is to obtain an easy and highly accurate measurement setup. Our fabricated PUF chips show an intended variation in capacitance and therefore generate characteristic fingerprints. We show that the parasitic capacitances and measurement variation are much smaller than the intended fluctuation of our PUF capacitances. This enables us to generate reliable and less error-prone fingerprints. Our presented measurement methods in combination with the technological PUF structures have shown to be accurate and reliable for flexible commercial application.